Larry D. Spears offers us this tip
I recently had a real near miss with an outdoor electrical extension cord at my home.
I had been using the cord while it was still rolled up on a storage spool.
Many times in the past I have unrolled only enough cord to reach the appliance I need to power. I felt this was a good practice in order to prevent a tripping hazard, and keep everything looking tidy and neat. However, electrical cords are rated in large part by their insulation factor. They are designed to be used in environments without extreme ambient temperatures such as what we normally experience on a day to day basis.
By not un-spooling the entire cord before each use, I had unknowingly altered the temperature the cord was exposed to tremendously.
The temperature in the center of this cord bundle became hot enough to melt all of the insulation from portions of the wire.
The first thing I looked for when I discovered this was a caution on the spool indicating the proper use of the device and there it was, molded right into the side of the spool “Caution: Unreel cord before use”. I am attaching pictures so you can see what I am talking about. Also, I am asking you to please send this to everyone in your distribution list so they will realize this is a very dangerous practice. So many people I have talked to about this do the exact same thing.
As you can see in the last picture, the portions of the wire that were exposed (that I could see) were not damaged. It wasn’t until I was unreeling the entire cord that I found this.
PLEASE stop someone if you see them doing something you know is wrong or unsafe. Even if they have much more “experience” than you. There are many ways you can respectfully explain to someone they are doing something unsafe, so use one of them and let’s watch out for each other.
Larry D. Spears
What Mr. Spears has left out of his post is the amp rating of this extension cord and the size of load he had applied.
I’m fairly certain for this kind of damage to occur, the cord had to have been grossly overloaded. A properly sized extension cord under load should not be getting hot whether it is coiled or uncoiled. Certainly not hot enough to melt the insulation.
Here is a table showing current rating and allowable extension length.
The table is wire gauge, the length, the maximum current and the maximum wattage (they use 125 volts, the maximum voltage rating, to compute the wattage).
16 gauge, 25 or 50 feet, 13 amps, 1625 watts
16 gauge, 100 feet, 10 amps, 1250 watts
14 gauge, 25 or 50 feet, 15 amps, 1875 watts
14 gauge, 100 feet, 13 amps, 1625 watts
12 gauge, 25, 50 or 100 feet, 15 amps, 1875 watts
For a more detailed discussion see this post.
The included photo is the evidence that counts. Illustrated is an electrical cable which displays evidence of being pulled & stretched beyong the length of original manufacture. This was likely caused by driving away from electrical service with extension cord plugged in, causing the streetching – which reduced the conductor size below rating specification, and tearing open the insulation layers.
This illustrates user incompetence, and is begging for an accident to occur.
Looking at the picture displaying the burned power cord it seems to appear twisted. This twisting occurs – and can damage- when cords are wrapped up using the hand and shoulder method. The way my electrician neighbor taught me to wrap cords is by laying them out as straight as possible and then looping with one hand grasping the cord while the other feeds the remainder. The end result is a cord that is not twisted.
I believe that the cord displayed had been erroneously wrapped prior to it being used on the reel.
Yesterday I grabbed my extension cord that was wrapped around a plastic spool, I unrolled about 20 feet of cable and left the rest in the spool, I plugged in my electric heater (Holmes HCH6150U triple ceramic)all afternoon. I detected the smell of plastic melting, the cord itself was cold before and after the spool but it melted the core of the spool, good thing I caught it on time before burning the house down.